The present invention is directed to an organic film having electric field switchable molecules.
Researchers at HP Labs have conceptually developed and significantly built a novel molecular switch capable of changing color from one state to another under the influence of an electric field. These concepts have been the subject of numerous patent applications and patents filed by the present inventors and their colleagues. In general, the color change occurs through a molecular conformation change that alters the degree of electron conjugation across the molecule and, thereby, its molecular orbital induced HOMO-LUMO (highest occupied molecular orbital—lowest unoccupied molecular orbital) states. In one embodiment, the conformation change occurs through field rotation of a ring or rings within the molecule. In this instance, the conjugation is broken, or interrupted, between the rotating rings, called rotors, and ring structures that do not rotate, called stators. The rotors have electric dipoles that induce rotation within a given field. A coupling group (e.g., acetylene) between the rotor and stator elements serves as a “bearing” and conjugation bridge between the rotor and stator. The infinitesimal rotor inertia and frictional resistance of the rotor allows color switching times on the order of a nanosecond based on models. A method to create bi-stable color states has been disclosed wherein planes of rotor-stator cells are spaced and superimposed to allow interplane rotor-to-rotor dipole latching. Such bi-stability allows a color state to remain stable, potentially indefinitely, in the absence of an electric field.
It is desired to provide a unique set of dye-like optical properties that make it ideal for applications such as electronic paper, paper-like displays, electronic books, projection displays and the like. Such embodiments and properties are described in a number of patent applications and patents. Desirably, the high color switching speed and bi-stable color state attributes of the molecular switch allows time-modulated grayscale, passive matrix addressed full motion color video imaging. These features are collectively disclosed in additional patent applications and patents.
Conformational change rotor-stator molecules have been disclosed for electronic switching and memory devices, while a novel rotor-stator molecule-based media has been disclosed for electro-optic switched disk memory.
More recently, polarization-type switching materials have been disclosed. The polarization-type switch comprises molecules that are chromophores capable of being switched between two tautomeric forms through the action of an externally applied electric field coupled through an acceptor-donor dipole incorporated in the chromophore.
Switch state bi-stability is highly desirable for each of the envisioned molecular switch applications. Switch bi-stability enables image and electronic memory archivability, eliminates pixel refresh addressing for lowest display, memory and electronic circuit drive power requirement, enables time-modulated gray-scale and passive matrix addressing. The bi-stable structures disclosed thus far require precise alignment and spacing of rotor dipoles and molecular self-assembly. It is therefore, highly desirable, to discover bi-stability schemes that are less structurally rigorous.